Sanitary or municipal wastewaters and many industrial wastewaters are generally characterized as having high concentrations of inert and organic particulate matter. Typically, this particulate matter is measured as total suspended solids (TSS) and particulate carbonaceous biochemical oxygen demand (CBOD), respectively. These wastewaters further typically include soluble organic matter, typically measured as soluble CBOD, soluble or particulate organic nitrogen compounds and ammonia, typically measured as total kjeldahl/nitrogen (TKN), inorganic nitrogen compounds (nitrites and nitrates), and organic and inorganic phosphorus compounds, typically measured as total phosphorus (TP). The sum of TKN, nitrites and nitrates represents total nitrogen (TN).
Increasingly, many countries throughout the world, including the United States of America, are imposing more stringent effluent discharge regulations and in many cases are requiring increased or near complete removal of CBOD, TSS, TN and/or TP from these wastewaters.
Compliance with these stringent effluent discharge regulations will require modifications and/or equipment additions to existing treatment systems, or incorporation of such modifications or equipment additions into the design of new treatment facilities. These modifications and/or equipment additions typically are capital cost intensive and generally result in significant increases in operating costs due to increased energy and chemical usage, generation of additional residuals requiring disposal (e.g., increased solids generation due to chemical addition to achieve complete TP removal), and an increase in the manpower costs for operation and maintenance of these increasingly larger and more complex treatment systems.
To-date, in many cases where plants have been upgraded to meet stringent effluent nutrient requirements (i.e., TN and TP concentration values), performance results have been variable. Accordingly, there remains a need for improved biological wastewater treatment systems designed to provide removal of organic and inorganic compounds.